Electrical switch and variable resistor for miniature electrical apparatus



May 19, 1959 H. J. GLUECKSTEIN ET AL ELECTRICAL SWITCH AND VARIABLE RESISTOR FOR MINIATURE ELECTRICAL APPARATUS Filed May 2, 1956 2 Sheets-5210014 m. INVENTORS HENRY J.6LUECKSTEIN CHARLES R. Gosne KARL W. YOUNGBECK May 19, 1959 H. J. GLUECKSTEIN ETAL 2,887,553

ELECTRICAL SWITCH AND VARIABLE RESISTOR FOR MINIATURE ELECTRICAL APPARATUS Filed May 2, 1956 v 2 Sheets-Sheet 2 '74 INVENTORS 3 HENRY J. GLUECKSTEIN 5,; 5 3 Commas R. Goene 4 KARL W. YOUNGBECK United States Patent ELECTRICAL SWITCH AND VARIABLE RESISTOR FORMINIATURE ELECTRICAL APPARATUS Henry J. Glueckstein, Brookfleld, and Charles R. Goerg and Karl W. Youngheck, Milwaukee, Wis., assignors to Globe-Union Inc., Milwaukee, Wis., a corporation of Delaware Application May 2, 1956, Serial No. 582,109

6 Claims. (Cl. 20155) This invention relates to improvements in electrical switches incorporated with variable resistors andespeciallydesigned and adapted for use in connection with miniature electrical apparatus such as hearing aids and pocket receivers.

Assemblies of this type of necessity must occupy a minimum of space yet the switch must be enclosed-andself-cleaning because in many applications of mmiature electrical apparatus dust, lint, hair, deposits from perspiration, and other foreign substances, due to the carrying of the device by people, collect on the switch and cause the malfunctioning of the butt or pressure contacttype of-switches.

It is an object of this invention, therefore, to provide a switch and variable resistor assembly totally enclosed whereinthe switch is self-cleaning and so assembled directly to the variable resistor that'a of space is required for the unit.

It is a further object of the invention to provide a switch and'variable resistor assembly the action of which is characterized by a distinct feel which indicates the off position of the switch.

A still further object is to provide a self-cleaning switch mounted on and operated by a variable resistor in which the'switch is electrically quiet during the operation of the resistor;

These objects are attained by providing a base in which is-rotatably mounted an operating shaft. One side of the'base supports a variable resistor of a conventional type controlled by the rotation of the shaft, such rotation being controlled by a knob secured thereto. 0n the'op trical contact therewith. A cam carrying member, di-- rectly mounted on the operating shaft, in-one position thereof has a single cam which engages the blade and holds it in open" position. In the"other"positions of the cam carrying member it is out of'contact with the switch blade assembly and will not disturb the switch as thec'amcarry'ing member rotates during operation of the variable resistor. The blade has a notch into which'the cam'snaps to provide a distinct feel when the switch has been operated'to its open position. The base has walls on opposite sides to which covers are cemented to enclose both the variable resistorandthe electrical switch. A stop member formed on the resistor side of the base engages as projection integral with the shaft to limit rotation at opposite extremes.

The electrical switch so constructed and incorporated with the variable resistor may be of extremely small size. The switch and resistor unit herein shown, exclusive of the knob, terminals and mounting studs, has an overall diameter of approximately .500 inch, and an overall approximate thickness of approximately .191 to .210 inch. In spite of such small size, the switch so incorporated with the unit has a wiping action which removes from the contacting surfaces any dust, lint, or other foreign substance which would be detrimental to the establishment of a positive electrically noiseless contact. As the switch is spring-biased to its closed position, and in such position the switch blade assembly is out of engagement with the cam as it rotates during regulation of the variable resistor, the electrical contact will not be disturbed, thus keeping the" switch as electrically quiet as possible.

The novel features, which are considered characteristic of the invention, are setforth with particularity in the appended claims. The invention itself, however, both as'to'its organization and'its method of operation, togetherwith additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which:

Fig. 1 is a view in side elevation of a variable resistor and switch embodying the present invention, part being shownin section on the line 11 of Fig. 2;

Fig. 2 is a plan view of the rear of the device of Fig. l with part of the back cover broken away to reveal the switch;

Fig. 3 is a plan View of the front of the device of Fig. l with part of the front cover broken away to reveal the variable resistor;

Fig. 4 is an enlarged fragmentary sectional view taken on'the line 44 of Fig. 2; and

Fig. 5 is an-enlarged fragmentary sectional view taken on the line 5 -5 of Fig. 2.

Referring to the drawing by reference numerals, the switch is moun'te'd on and incorporated with a small variable resistor especially adapted for use in connection with miniature electrical apparatus such as hearing aids and pocket receivers. The variable resistor is of convention'al'design. It is mounted on the left side (as viewed in Fig. l) of a'dividing wall 10 of acup shaped molded base havin'g' peripheral walls 12 projecting from opposite sides of such' dividing wall. It'includes a resistance element 14'on which rides a-spring contact 16. This spring contact is: staked to a shaft 18 rotatably carried by the dividing wall 10. The shaft 18 has a central portion 20 loosely mounted in a bearing 22 in such interior wall. The shaft is held in place with spring'contact 16 deflected to produce desired pressure by a C-n'ng 24 in an annular groove 26 in the shaft on the opposite side of the dividing wall 10. A collector 28 resiliently engages the shaft 18 and makes an electrical connection between it and terminal 30. The opposite ends of the resistance element 14 are connected to resistor terminals 32 and 34. The rotation of the shaft 18 is limited by a lug 36 integrally formed onan annular web 38 on such shaft engaging op posite ends of a molded projection 40 having an angular length of substantially The shaft construction is unique in that the lug 36 is made by blanking it from such'annular web. This limiting structure is positioned radially inwardly of the resistance element 14 and utilizes space which would otherwise be structurally present even if notso employed. The variable resistor is enclosed by a front cover 42 cemented to the peripheral wall 12. It may have fingers 44 which interlock with'notches 46 in such' wall to prevent rotation and provide a fixed position of assembly. The shaft 18 projects through an opening 47 in such cover to provide an additional bearing for such shaft.

The electrical switch is mounted on the right side (as viewed in Fig. l) of the dividing wall 10. It includes a pair of terminal forming studs 48 and 50 which are riveted to the dividing wall 10 as shown. The outer ends of these studs project beyond the peripheral wall 12 and are threaded for customary usage of mounting the device and attaching conductors. A switch blade 52 is pivotally mounted on the stud 50 between the dividing wall and a shoulder 54. A coiled spring 56 with extensions surrounds the stud 50 between the dividing wall 10 and the switch blade 52. It has one extension pressing against the peripheral wall 12 and the other hooked to engage the outer edge of the switch blade 52. The spring thus urges the flee end of the switch blade to the right and downward as Viewed in Fig. 1. The coils of the spring 56 are under compression so that the blade 52 is forced against the shoulder 54 making a good electrical contact with the stud 50. On the free end of the switch blade 52 there is a knife edge 58 which engages a convex portion 60 on the stud 48 as such end is forced downwardly. The slope of this convex portion is inward and terminates in a cylindrical section 62. As the coiled spring forces the switch blade 52 downwardly from the position shown in the dotted lines, the knife edge 58 will wipe the portion 60, slide down it, and come to rest on the section 62. This positive wiping engagement between the switch blade and the terminal stud keeps the contacts clean and always insures good electrical contact.

The switch is moved to open position at one end of the rotation of the shaft 18 by a switch actuating cam 64 made of insulating material and fitted on milled flats 66 on such shaft. The cam 64 has a nose 68 which slides along the lower edge of the switch blade 52 to raise such blade and break its contact with terminal stud 48. The blade has a notch 70 in such lower edge into which the nose 68 slips at the end of its travel to provide a feel indicating to the user that the switch is in off position. The notch also holds the switch in such open position against casual operation. After the switch blade 52, at the beginning of the travel of the variable resistor, has made contact with the terminal stud 48, there will be a continuous clearance between the cam 64 and the switch blade 52 during the remainder of the adjustment of the variable resistance. The contact thus made will not be disturbed during the rotation of the variable resistance. The switch is entirely enclosed within the molded base by a cover 72 cemented in place and having openings accommodating all the terminals. The cover 72 also functions to keep the cam 64 in proper place on the milled flats 66. The molded base may have a pair of laterally projecting lugs 74 which act to locate the unit on a panel on which it is mounted when the studs 48 and 50 are not used for such purposes and an adhesive is used instead.

Although only one embodiment of the invention is shown and described herein, it will be understood that this application is intended to cover such changes or modifications as come within the spirit of the invention or scope of the following claims.

We claim:

1. An electrical control device including an insulating base, a bearing in said base, a shaft rotatably carried by said bearing, an elongated terminal stud positioned on said base and projecting laterally therefrom to provide a side forming a fixed contact for a switch, a second elongated terminal stud mounted on said base and projecting laterally therefrom to provide a switch blade pivoting portion, a switch blade pivoted on said portion and swingable toward said shaft to engage the side of said fixed contact, spring means urging said switch blade toward said shaft and outwardly of said base, vmeans on said fixed contact directing said blade inwardly with respect to said base upon engagement therewith, and a cam member mounted on said shaft and having a nose positively engageable directly with sm'd switch blade for a small portion of the total rotational movement of said shaft to move said switch blade to open position.

2. An electrical control device as claimed in claim 1 in which said switch blade has a notch therein engageable by said nose to provide a feel of the open position of said blade.

3. An electrical control device as claimed in claim 1 in which said second stud has a blade engaging shoulder and said spring means forces said blade into continual electrical contact with said shoulder.

4. An electrical control device as claimed in claim 1 in which said means on said fixed contact comprises a convex portion sloping inwardly toward said base and said blade has a knife edge engaging said convex portion and sliding therealong to provide a wiping action.

5. In an electrical control device an insulating base having a variable resistance compartment and a switch compartment separated by a dividing wall integral with said base, a bearing on said wall, a rotatable control shaft carried by said bearing and projecting into each compartment, a resistance element carried on one side of said wall in said variable resistance compartment, a spring contact secured to said rotatable shaft and riding on said resistance element, a projection in said variable resistance compartment extending laterally from said wall, an integral lug on said shaft engageable with opposite parts of said projection to provide limits for the rotation of said shaft, said projection and lug being positioned radially inwardly of said resistance element, a cover enclosing said variable resistance compartment and having an opening through which said shaft projects, said opening providing an additional bearing for said shaft, a fixed contact terminal stud secured to said wall and projecting from said switch compartment, the side of said stud forming said contact, a second terminal stud mounted on said dividing wall and projecting from said switch compartment and having a switch blade pivoting portion, a switch blade in said switch compartment and pivoted on said portion and swingable toward said shaft to engage said fixed contact terminal stud, spring means carried by said second teminal stud and urging said switch blade toward said shaft, a cam member in said switch compartment mounted on said shaft and engageable directly with said switch blade to move said blade to open position as said lug comes to rest on said projection, and a cover enclosing said switch compartment and holding said cam in place, said cover having openings for said terminal studs.

6. An electrical control device as claimed in claim 5 in which said fixed contact terminal stud has means directing said blade inwardly with respect to said wall upon engagement therewith and said spring means also urges said switch blade outwardly of said wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,039,117 Schellenger Apr. 28, 1936 2,320,837 Turner et al June 1, 1943 2,350,277 Grimes May 30, 1944 2,572,651 Mucher Oct. 23, 1951 FOREIGN PATENTS 664,257 Great Britain Jan. 2, 1952 

